This is the age of hi-fi, jets and computers. Rapis advancements in science and technology have made their impact on the printing industry of the world too. The old techniques of printing have become obsolete and made way for the new technology. The book contains the latest printing processes like web, gravure, flexo, security and offset printing. This is very useful book for new entrants, technicians, craftsmen and executives working with printing industries.
MODERN PRINTING PROCESS
INK-JET
In the past, the quality of- ink-jet printing has not been good enough to prevent the recipients of direct mail products from throwing them unopened into the dust bin. If the mailshots are accompanied by the wrong name, house number, or post code, one can hardly expect a positive response to the advertising messages contained there in. No wonder then, that the main experts (technologists) in ink-jet systems for graphics arts applications, including Domino, linage. Scitex Digital Printing and Videojet, are Constantly striving to improve speed, quality & accuracy.
Now-a-days, the majority of personalised direct mail ink-jet printing, has been in mono with the occasional use of spot colour. However Scitex Digital Printing, is emerging as the pacesetter for developments in highspeed, high quality, four-colour ink-jet technology. The other manufacturers are showing evidence of lower-cost developments.
Scitex Digital Printing demonstrated a prototype full-colour (CYMK) digital press, based on continuous-flow ink-jet imaging. This technology will result in full-color 100% variable printing systems, that will provide fast set-up, quick turnaround, letter quality, direct-to-paper digital printing with variable output.
Colour images are produced by printing droplets of Cyan, Magenta. Yellow and Black on top of each other. This technology prints with multiple dots, at each pixel location, giving exact control ot colour and density.
Colour depth and saturation are also said to be enhanced by this process. A potential single row of jets is provided to enhance edge definition, registration and positioning.
Suppliers have already promised for a device with low operational costs and speeds, That will considerably exceed the 200ft./mm. demonstrated Development is in the early stages.
Benefits include complete variability of layout, contents and graphics, compatibility with industry standards for page layout and data transfer; the flexibility to set up and print jobs, ranging from short runs to high volumes on the same equipment. In addition, it gives the ability to personalise every document and to offer high-volume production at a low cost per page.
However, not every one will have a requirement for four-colour ink-jet print, nor be able to afford the press, which is expected too costly. Of greater concern the other ink-jet suppliers is improving the speed, resolution and flexibility of existing technology.
Until the new press is available, ink-jet equipment prints only black-and-white or spot colour. It serves the commercial printing, business fon-ns, direct mail, promotional graphics, catalogue magazine, lottery and gaming industries, as well as inplant printing and mailing operations. This is taking white paper at one end of the production line and transforming it into a full-colour, personalised and innovative leaflet or mail shot. Because -this takes place in one continuous operation, optimum cost-effectiveness is achievable.
The ink-jet print head have been added to Zirkon eight-page four & five-colour mini-web presses. Digital printing offering customers the benefit of two komori 16-pages web presses able to personalise products, as well as an 8-pages Heidelbery-Harris. It is able to print, personalise and inline finish in excess of 45000 products an hour, all in one pass. The three systems can all personalise in red & blue as well as black on both sides of the web. Most continuous stationery producers tend to personalise on just one side, due to cost implications and finish as a separate operations.
Ink-jet had come a long way from its original application for straight forward product identification. Ink-jet is no longer confined to Coca-Cola bottles. The technology has left this market and is offering versatility and creativity to markets previously not involved in ink-jet. With the capacity to print upto 40 inch width from a combination of one and 4.25 inch heads at speeds of 1000 ft. a minutes the quality and flexibility can now offer is out standing.
Magazine publishers are now able to personalise their products on the outer wrapper and inside and have a full-selective capability. Postal codes and addresses are printed on the wrapper, while two personally-addressed coupons are added to the back cover containing e.g a 10% discount on any tickets and a special offer for a Sunny’s cricket bar.
Such capabilities could also be of benefit for subscription renewals or to encourage a higher reader response to advertised products, by supplying a ready printed card containing readers details so that they don’t need to spend time filling it in themselves.
This level of sophistication is only possible through powerful control systems, which operates ink-jet printers to provide inside/outside addressing, personalisation, numbering and postnet bar coding.
Suppliers also offer the smaller editor 2 multi-position ink-jet controller for up to 24 print-heads, providing upto 48 lines of print, An extensive range of fonts and graphics is available, enabling numerous messages to be printed. One of its advantages is the ability to control multiple print heads located in different areas of the production line.
Ink jet print-head can be used to reproduce a veriety of bar codes, fonts, usergenerated graphics, logos and photographs.
Image also acknowledges that the way forward for addressing or using ink-jet, is to achieve higher resolutions, and multiple fonts, readable in postal, equipment, which are becoming essential with the higher speeds of mail handling system
As ink-jet improves in accuracy, resolution and speed, of mail handling system the only limitation to its wider use in commercial printing applications is the imagination of.the end-user.
Ink-Jet
Image sprayed on to the paper with water based inks.
Many different ink formulations including inks with etching or acid bases for printing on coated stock.
Problems: since they are water based, the images will smear if they were to get wet.
Since ink is water based, sometimes it is absorb ed into the paper, resulting in a weak image.
Since ink jet produces bar codes through a sprayed image, bars formed at higher densities (closer together) become more difficult to read correctly. Upto700sfm.
Laser
Light impacts on photo-sensitive, hollow cylinder or drum. Laser beam hits and comes off a 6 or 12 sided prism and rotating mirror.
The beam of light rotates to the drum, swinging from the operators side to the gear side for one full, line of image, usually 240 dots per inch in both height and width.
The image, exposed to light, is on the drum. Drum rotates to a hopper containing toner with developer, then rotates to the paper, and, usually1 a corona wire (on the reverse side of the papei-) pulls the image off the drum onto the paper.
Image is then treated by heat (either a pad from the back side or infrared light above the printed image).
Images are usually more on the gray side. Image sits on top of the paper and does not impregnate the paper.
To protect image, coating the bar code is recommended.
The printed image is light black or gray. The larger the image, the grayer it will be because of the inherent nature of the photo sensitive drum.
Average, speeds from 90 to 130 pages per minute.
Ion Deposition
Image cylinder holds the image to the surface with an electrical charge.
The image head is a-hollow tube or chamber, with a small hole in the bottom. The air in the Chamber is electronically charged separating plus and minus Ion’s. The minus or negative Ion’s leave the chamber through the hole in the bottom.
The (-) negative ion’s, place strokes or images on the image cylinder to create a negative image.
The image cylinder rotates to a hopper containing toner. The negatively charged ion’s attract the toner to form the image.
The image cylinder rotates and transfers the image to the paper as it passes by.
- Under pressure: 200 Ibs per linear inch.
- Shears: There is 1 degree angle between the impression cylinder and the image cylinder, so that the character image is sliced off on to the paper.
- As in the laser process, the image sits up on the paper and should be coated for protection.
Speeds run from 90 to 130 pages per minute and much slower.
Manography
Honey well bull engine is the hardware Print head (Coil) generates a square spot on a drum which rotates to a chopper containing toner.
Toner is then magnetized in the hopper and applied to the image on the drum.
The drum then rotates to the paper, at which point a corona wire with an opposite charge will pull the image off the drum on to the paper. It is then heat set.
Problems: When the toner is fused, it will fuse to itself.
The image sits up on the paper and will not impregnate the paper itself.
Image can chip or break off.
Sometimes there is teflon in the toner to help in the fusing process. This prolongs the life of the print head, but the chemical reaction harms the corona wire.
Finish the form with a protective coating. 90 pages per minute (approx. 82.5)
Led
Led-Light emitting diodes
Similar to the laser. Has a photo sensitive drum. Image head is similar to a bar print head with pins or grids, The diodes light the readout in a sequence as the drum passes by.
Image cylinder sees the image and takes it off the drum. Voltage is either increased or decreased. The cylinder rotates to a hopper with an electrically sensitive toner, which is attracted to the image charge.
It transfers the image to the paper using a corona wire with the opposite charge. It is then heat set.
Very slow. Only one company (Japanese) selling in the U.S. Breaks and chips. Only 5 to 7 pages per minute.
Thermal Direct
Special heat sensitive paper. Print heads are a series pins that heat up and once heated, the pins impact on the paper burning a black dot where they touch the paper.
- Customer/Lose time heating the pins in the print head.
- Only a narrow imaize area (Approx. 4").
Thermal Transfer
Uses a wax or poly-based ribbon. Normal papers can be used. The image head is heated and image released to the paper from the ribbon.
Advantage over thermal direct is the lower cost of paper and its shelf life. Very, Very Slow; Much slower than the laser.
Film Plotting Machine
This is the final station of the process. Once the design is approved for.printing, plate film must be created. This machine uses a small laser beam to expose film a resolution of 2,540 lines per inch. It produces negatives upto 34" x 48". Digitized information from the electronic imaging unit is networked to the, film plotter, where it exposes each negative to produce each colour of the design. This is the first point at whicfifilm has been created throughout the entire process.
Basically there are two types of plotters: (1) flatbed plotters, where film is laid flat and then electronically laser exposed and (2) drum type platters, where film is hung and then wrapped around a large drum that spins and is laser exposed while turning.
Each of these electronic stations, when net worked, form a complete design-to-platcready film system.
Suppose a customer has an idea for a design. The customer can draw a rough sketch. If the customer is in Calcutta or Varanasi and the engraver is in New Delhi, the customer can fax the sketch to the engraver’s electronic art station.
Fax in hand, the design station operator can scan the black and white fax into the electronic art system of the desk top scanner and send it to the design station. The image is now on the screen in a matter of minutes. The operator now can smooth rough edges, set type and position the type in the right places. Type can be curved, wrapped around irregular shapes or set flush left or right.
Once all the copy is in position on the screen, the operator assigns colours to the elements. The screen on the design station has all colours available to it. A colour wheel can be displayed on the screen, allowing the operator to mix and match his own colour.
Once colour are assigned, the design is ready to be proofed. The digitized information is sent from the design station to the digital proofer, where a proof is generated depending on the complexity of the design, this can be done in less than an hour.
The customer has a colour proof very quickly, with a minimum of time and money invested because no film, stripping or separation have been made.
Another benefit of the electronic art system, is the ability to design on 3,1/2" floppy disks. If a design requires promotion or revision, the previous version can be called upon the system, revision made and either proofs or plate-ready negatives created.
Once the proof is approved, we can begin to create a high resolution file on the computer. Remember that what we scanned in on the desktop scanner was low resolution and only for design.
Now we can scan in transparencies or reflective art on our high-resolution, four colour, scanner. The scanner then networks the colour separation to the electronic imaging unit, where it’s colour enhanced. The separating is then sent to assembly unit, where it is electronically stripped together with the type and art created on the design station.
Black & White mechanical elements that were low resolution scanned for design on the desktop scanner e.g. company logos, must now be scanned in on the high-resolution scanner and net worked too the assembly unit for positioning in the design.
The design is now ready to be digitally networked too the ink jet proofer. The important thing is that now we have made a proof of four-color process and line copy without generating any negatives. If changes are required, we simply manipulate computer information and can then generate another proof. Once the proof is approved, the design is ready to be made into film negatives. The design is now networked to the high resolution computer film plotter.
Some customers are setting up low resolution design stations in their own plants and through a telephone and modem are looking into the trade shop’s high resolution electronic imaging system. This technology allows the printers to do their own design in the shop, by using the inexpensive desktop scanner and design station.
The best thing about the electronic system, is the ability to hook up low resolution, front and equipment that is cheaper to run rather than the very expensive, high resolution computers and film plotters.
This systems takes a lot of the graphic burden off the high-resolution equipment and puts it on the front-end, low-resolution equipment, where designing is cost efficient.
COMPUTER TO PLATE TECHNOLOGY (CTP)
Today big printers are investing in computer (CTP) systems that by pass film entirely. With electronic imposition of complete flats, it makes sense to go a stage further and expose plates instead of film, eliminating several prepress production stages.
Imaging directly to plate also does away with the distortions introduced in film-based plate making. It is possible to resolve fine image detail more consistently, which is a special benefit with frequency-modulated screening where very small spots are being imaged.
Offset plates are quite thin. If the base material is flexible enough, they can be loaded in an imagesetter in roll form and exposed. Alternatively, dedicated plate exposure units commonly known as platesetter can be used for metal plates. These systems can in corporate automatic register punching.
Sometimes CTP loses out to conventional film-based platemaking due to the speed and low capital costs of conventional platemaking equipment. e.g. When duplicate plates or reprints are needed, a CTP system has to repeat the imaging process, while a conventional platemaking system has only to re-expose the film. Film is a convenient storage medium that is cheaper than archiving rasterized data on magnetic media. Proofing can also be a problem unless digital proofs are accepted as contract proofs.
It is not possible for every element in a job to be supplied a digital form, and then it is necessary to combine film produced conventionally with the digital data.
The platesetter receives the imposition instructions and exposes the digital information, masking the areas that are missing. The device then uses the register marks as a guide to position the films & expose them conventionally.
Computer-to-plate technology (figure Y) eliminates the film output and stripping stages (Figure X) in the production workflow.
Alternatively, film or artwork can be scanned and converted into digital form, Very high resolution scanners are used to avoid image quality loss on line artwork, such as type with fine strokes and to avoid the need to descreen halftones, which risks changing color values. One type of scanner designed for this purpose converts the scanned data directly in postscript code, which can then be inserted into a postscript CTP workflow.
Film is a convenient storage medium that is cheaper than archiving rasterized data on tapes or optical discs.
When alternations are required the new matter is either stripped inmanually or the films are re-output. It is more or less impossible to edit rasterized CPT data. Changes must be made to the customer files and new plates produced whenever alterations are required.
Platesetters are usually very large as they must be able to handle the full plate size for a given job plates cannot be assembled from strips like films). Some models incorporate automatic plate handling mechanism ana can accept plates upto 48 x 66 inch i.e. 1200 x 1650 mm. They ay incorporate work flow management, including queing in and preparing files while the previous job is being exposed, automatic compensation for shingling and placement of colour bars, register marks and fold and trim marks. These systems at the very end of the prepress production workflow, are installed at printers or occasionally at larger trade shops.
In contrast to conventional photographic method in which the whole plate is exposed from film simultaneously, in direct - to plate system must be more sensitive. Such containg are to sensetive to handle in daylight and unlike convention plates, they must always be handled and loaded in the dark.
By using high-sensitivity plates and multiple blue laser exposure heads, exposure at 4000 dpi can be similar to those for conventional diazo and photopolymer plates.
Computer To Plate
It is not all that long ago since publishers supplied manuscript Or typescript for the typesetter to re-key. Indeed some still do - but with the advent of Computers and universal languages like Postscript an increasing number of authors and publishers do their own key-stroking and page make-up and supply the printer with a disk for outputting on to bromide or film.
A number of prepress houses are now able to offer a CTF (computer. to film) facility which involves outputting eight pages of AS on one piece of film already imposed with correct heads, backs and gutters. Four of these are then exposed on a Stoesser print down frame for platemaking in very quick time. Some imagesetters are able to go from disk direct to 70mm film for automatic imposition. One of the problems are the moment is that generally speaking image setting film is much more expensive than negative film for platemaking. However, that situation is unlikely to continue. The aim has got to be to avoid the use of film altogether.
This brings us to a consideration of CTP (computer to plate) and as the technology evolves so some platemakers are struggling to keep up. CTP involves the customer supplying an electronic disk in Postscript or similar so that the prepress supplier can use this to go direct to plate thus avoiding the use of bromide and film altogether (see Figure 1).
There are at least two solutions available on the market that address large format press sizes and these are from Krause and Misomex. Interestingly they approach the problems in quite different ways. The essence of such solutions is that the disks supplied should be as Postscript files created using QuarkXpress, PageMaker, Ventura and other software packages. When disks are supplied they should be accompanied by laser proofs to ensure there are no conflicts between systems and no surprises when the job is printed. No doubt, as confidence in CTP grows laser proofs will be redundant and publishers will use unaccompanied data transmission “over the wires”.
The Krause solution involves RIPing individual rates and storing the subsequent bitmap on the PSU (page storage unit). At that point the information is read onto exabyte tapes each usually containing one complete book. The tape is then kept until the plates are required at which point it is read onto the IPU (imposition processing unit). Once the imposition parameters have been installed the plates are loaded onto the platemaker and the plates exposed and processed ready for use on the press. The exabyte tape can be stored in a tape library for future use as required for reprints.
Nervous publishers will be able to see a proof before plates are made but obviously this will slow down the whole process and the use of a large plotter is necessary to produce the proofs.
The approach taken by different manufacturers in exposing the electronic bitmapped data direct to the printing plate is interesting. The Krause solutions involves a large and heavy platesetter with about 5 tons of granite in the framework to give stability to the laser. The plate, up to SP65 size, is loaded on the concave bed and slowly moves underneath the laser which exposes the image through a prism onto the plate. The technical data and plate exposure times for the Krause Laserstar are presented in Tables land 2 respectively.
The Misomex solution is based on their step and repeat system. The laser head is clamped by vacuum on to the plate and four A5 pages can be exposed at one time. The head then moves (rather than the plate) andexposes the next four pages. There are of course pros and cons for each solution but at this stage Misomex claims that their system is almost twice the speed of the Krause system. That of course is not the whole story Misomox are working with Cascade in developing pre-platemaking protocols and hope to have an actual system to show shortly, while of course Krause already has systems in the USA and Europe working in printing plants.
Savings are achi avable in time and cost due to fewer people being needed, of course, without the intermediate film, higher quality can be achieved as well with help from Misomex, Create Publishing Services and Redwood Books (both BPMG companies) cooperated to produce their first CTP book in the sununer of 1994. This was a book of old photographs and text and the quality achieved Was mi than similar books produced conventionally.
A continuing and unresolved problem is the limited suppliers of plates and the price being asked. The main supplier to users of existing Krause systems is Kalle, but they propose to market their plates in the UK at about 50 per cent more than the price of conventional plates. The same plates are available from the same supplier however at very much cheaper prices in Ireland and even more so in Germany and Sweden!
However, other suppliers are working hard to break this present monopoly and these ind)ude Polychrome, Ou Pont, Horsell,,Fuji, Agfa and others. However because of plate technology some will work better than others on the two systems. For example the laser on the Krause platesetter is strong enough to be able to penetrate and expose onto the N90 plate but could be too strong for other plates. No doubt as systems are installed increased demand will drive down prices as will increased competition and both Misomemx and Krause will develop their systems to work with the various plates.
This then bodes well for book manufacturers and for book publishers who will need, to work closely together to extract the major advantages this front end revolution has to offer.
CD ROM
A short while ago CD ROM was unheard of but now everyone has the word on their lips. Purchasers of home computers insist that the facility is available on their hardware and publishers of books are now among those rushing to fill the newly created opportunity. A number of large UK publishers including Dorling Findersley and O.U.P. are now producing titles on CD ROM. DK published five in 1994 and a number are already on stream for next year. Part of the excitement will be, for example, to see blood flowing through veins in the diagrams of the human body.
On the other hand having seen this sort of thing once who will want to see it again ? Overall the CD ROM facility will best be used for journals and for dictionaries, directories and other works of reference. This is servicing a new, and growing market and should not impinge too strongly on the traditional book market. It is estimated that strong growth over the next three years will mean that many books will be marketed through this medium.
Printing
Digital printing for monochrome and colour is now offered as a solution to very short run printing requirements both for loose leaf and conven-tionally bound products. Suppliers such as Indigo, Heidelbery, Exikon and Agfa are now offering presses which are able to accept digital data. The first Indigos for bookwork in the UK are at Eastern Press and other companies are watching this initiative with interest.
The Rank Xerox Docutech is now well established as a means of producing short run books. A number of these are in operation at book printers engaged in printing small numbers of publishers out of print titles, which are finding new in the market place.
The more conventional means of book production on large perfect-ers and web offset presses seems to be growing too. While no longer available the perfecters are nevertheless still being built. Both the Sovereign and finding purchasers too. Second hand presses are still in demand.
Short run colour, around 4,000-10,000 copies, is an area yet to be fully exploited Jarrold are investing in this market and will shortly be joined by one 4 companies aiming at producing short runs of the very highest quality print, of stochastic screening and waterless printing will continue to drive quality stan even higher. Webs for monochrome and two colour books are now also well establish. The front runner is of course the Timson T32 press and developments are am from Strachan and Henshaw who have not really been able to convince the rr that the Variquik press is the way forward.
CTP is not a separate, stand-alone technology. It is a part of an entire electronic operation. CTP can simply be thought of as an advanced output application printers with largely conventional prepress operations will experience massive work-follow distribution, trying to step into CTP in a long or To ensure a smooth transition and high probability of success, conventional prepress operations would be well-advised to implement a gradual chantre over process. There are three stages in this process-two page film image setting (composed single pages & spreads, imposed full-size signature four or eight page) film image -setting, and plate setting.
Each stage requires a certain technology, and the technological infrastucture is cumulative the technology of each stage builds on that of the previous step.
The first step towards CTP is proficiency with baste colour electronic prepress, including output of composed single page and two page spreads Requirement for the are as follows:-
Colour image input bringing a colour image into the system as an image file requires a digital scanner of some sort of a digital catnera.
Simple networking. Image setters and their RIPS require a networking environment in order to exchange files with one another. Either is the most common protocol for small networks such as the baste electronic prepress operation. It provides theoretical speeds of up 10 million bits of information per second, though typical real world throughputs are much slower.
Trapping. Traps can be applied by desktop trapping packages, RIP-based trapping modules or high-end work stations. -
Post script capability. Virtually all major desk top programmes and output devices employ the postscript page description language.
Digital page assembly. This is where layout takes place, since the purpose of all these stages is the output of complete pages, digital page assembly is essential.
Digital colour correction. Simple image retouching is the most common form of colour correction. It is a prerequisite for any type of sale able commercial colour.
Next is the out put of imposed film files, which requires the addition of a large format image setter to the system. In terms of learning and capabilities. This is probably the largest single step. For many printers, this stage will actually comprise two stages-formatting and eight-page film setting. However, printers who plan to use only, smaller formet presses like 20 × 28" sheetf ed or eight page webs, will stop at the four-ho plan to use only 40' sheetf ed and or 16 page web will probably want go directly from 2 page image setting to 8 page imposed film.
To be effective, the large format image setter must be supported by several new capabilities.
Open prepress interface (OPT) refers to the ability to use a low-resolution version ned colour image for page make-up and image-placement, replacing it with full-out resolution scan at the moment of out put. This is essential for efficient operation is a largely Macintosh or PC environment. High resolution colour large for Macs & pcs to handle comfortably and will show a typical ethemetlocal area network) to an unacceptable, level, ition capability allows the correct placement of individual pages within a master s operations find themselves handling both desk top pages and pagesprepared by a high-end system. It is, therefore, desirable that an imposition prograrmme to be able to handle both types of pages in a single imposition.
Up to this point, colour proofing needs can be adequately met with a conventional (analogue) colour proofing system, possibly bolstered by a desktop digital f. Before taking the final step into direct-to-plate production, however. Dupont believes it will be necessary for the printer to install contract digital colour proofing and educate customers in the use of these proofs.
The most courpicuous difference between the imposed film stage and full CTP is totally reliant or a proof.
At present, some printers are dealing with this by running parallel analogue and digital proofs of the same job and showing them both to customers. This assumes that the digital and analogue proofs are tightly calibrated, which is absolutely essential. They must both also give a close match to the final press sheet. Of the pioneering printers Using CTP methods, many claim that moving to computerized platesetting, while a major step, is not as critical as the imposition and digital proofing stages. Itdoes, however require the addition of its own enabling technologies:
A platesetter is essentially an imagesetter capable of handling metal plates.
Advanced networking. As platesetters are integrated into the production network, the volume of data increases dramatically. Standard Ethernet networks arc inadequate for high-volume operations, which should use higher performance networks such as fast ethemet, ATMs and FDDI.
Electronic press control bars are an important requirement of the CTP work flow. In a CTP environment, they are generated electronically and must be exposed in the proper position an each plate. In addition to their traditional functions as devices to monitor print conditions during a press run, these colour bars will also be used for calibrating the platesetter to ensure consistency between plates.
Undoubtedly, CTP is the wave of the future. To use its maximum benefits printers need only take care to approach computer to plate methodically and with fuH awareness of the steps involved.
TP or not ?
The number of computer-to plate systems on offer is growing almost daily. Brand name identification in some cases is becoming confusing. Even competitors on the supplier side are earning OEM agreements. Gerber uses pressetech for the latest unit which, like systems from Greo (Trendsetter) and optronics (Aurora) are bringing prices for CTP systems, albeit primarily in the smaller A3 format, down to under USD 100000.
Du point study in North America has found that more than 60 per cent of printers there have no plans at present to invest in CTP. The companies switching over are mainly large groups like Donnelley, Quebecor, publishers.press and specialist book printers and producers of manuals. Black-and- white users for the time predon-dnate.
PDI announced a CT system for bimetal plates.
Polyesters plates have gained in plate life, quality of images and should be considered for CTP applications” says Denis Mason, a US print consultant. In his view these plates, together with the new budget price systems, could appreciably speed the spread of CTP use,
Misomex-5040, SR, as well as systems from Krause and pump are specially designed for CTP applications in package and folding box printing.
Creo and Mitsubishi printing presses have linked up to offer complete colour profiling and management from digital platemaking via ink setting and press control to even integrated finishing operations. Heidelberg Data control is also -like MAN Roland pecomcovering the whole gamut of controls from pre-press to finishing.
Telecom giants like AT&T and sprint offer communications systems for CTP user so that from one digital entry point remote platemaking at print centres worldwide become instant.-Donnellely have developed an interface program for such applications.
Plates & Films
Specially formulated to meet the requirements of stochastic SC reening are Anitec Craftsman Ultra offset plates. Western Lithotech, now part of Mitsubishi Chemical, has a new range of Diamond two-side coated plates for “almost waterless” printing and LAI and LY-1 laser/exposure digital plates for use in imagesetters and direct platemaking.
Polychrome has teamed with Toray in Japan to offer CTX thermal plates, made by the polychrome plant in Columbus GA. The waterless plates are available for both conventional ard laser exposure.
Brazil’s IBF plate and film manufacturing company, celebrating its 25th birthday, has developed good markets especially for plates in North and South America, as well as Britain and continental Europe.
Gerber, Creo and optronics offer CTP systems for thermal plates for these systems for an those Kodak and (soon) 3M, too.
Dry film processing, pioneered by xerox verde and now polaroid is on the M-7-i-ch. Linotype-Hell introduced the Drysetter for the latter system. This manufacturer also presented a 16 -page CTP system utilizing Delta technology including post script Level 2 interpretation and screening. The system is available initially for Herkules. Quasar, Drysetter and Chromagraph R3060. The German manufacturer also announced thatover 1500 Topaz colour scanners have been sold so far. The new Topaz Robot flatbed transparency scanner allows batch scanning.
ECRM introduced the knockout 4550 laser imagesetter for colour work, apparently based on a Konica engine Monotype/Scangraphic Express Master that enables complete colour newspaper pages to be produced within 40-60 seconds.
Dalim, who have gained Dr Lutz Thiele, who was formerly on the board of LinotypeHell, as CEO, offer systems facilitating ideas, such as Twist, which permit different prepress systems to be run compatibly.
Eschar-Grand, of Canada, who have just opened a European branch in Belgium also (offer systems solutions. Pantone Hexachrome, the six-colour system, can now be proofed via Agfa.
SCANNERS
Select Scan
Select Scan’s high density range of 3.6 0 and maximum resolution of 4000 ppi enables it to produce scans comparable in quality to that of top-of-the line drum or CCD scanners. Its 6000-element, linear array CCD registers 16 bits per color data capture, providing superb detail even in the darkest of shadow areas. Select scan’s convenient flatbed design and offline mounting capabilities allow it to meet the high productivity requirements of commercial printers, service bureaus, color trade shops, and others, Incorporating the most advanced CCO technology and specially designed optics and lenses, Agfa Select Scan delivers superior image sharpness and color fidelity with every scan, making it the perfect scanner for producing high-quality advertisements, magazines, and catalogues.
Features
Select Scan provides two levels of scanner driver software applications: Fotolook for simple yet effective scanning operations, and Select Scan 1.0 for sophisticated scanning controls, like selective color corrections unshap masking and smoothing etc.
Selective color corrections during scanning to minimize the need for subsequent image manipulation.
- 16 bits per pixel for deep shadow detail.
- State-of-the-art aspheric illumination lens for scratch and dust minimization.
- Unique custom lens system to scan images at any resolution up to 4000 ppl.
- Single or batch image scanning with simultaneous off-line mount ing using additional slide holders.
- Slide holders that handle various film formats.
- Extensive documentation including Agfa’s acclaimed An introduction to Digital Scanning guide.
Horizon plus
Horizon plus is the impressive successor of Agfa’s popular Horizon scanner, which is in worldwide user by thousands of prepress professionals. It has been developed using the latest electronic and optical technology.
The Horizon plus is a versatile flatbed CCD scanner, designed both of reflective originals up to A3 forinat and transparencies as large as 24- cm x 34 cm. The ability to “batch” scan multiple color positive and negative films, color, grey scale and lineart reflectives, and even screened originals,provides outstanding flexibility and productivity.
Horizon plus scans color originals even faster than its predecessor. Set to speed mode, scanning .sup to 200% faster than the normal mode.
With a resolution of up to 1800 ppl in color, significant enlargement of originals is possible without noticeable quality loss. Thanks to its 36 bit color depth and 3 range, Horizon plus captures even the smallest tonal variations in any color images need to be printed in black-and-white a neutral density filter provides perfectly balanced results.
The redesigned focusing mechanism and improved optical components transfer maximum image detail into digital format. Where sharpness is lacking in original images, variable unsharp masking (USM) is adapted to scanning resolution, contrast levels and image density. Details are sharpened without emphasising grain or running shadow areas. The Agfa Foto Look scanners interface provides automatic or manual contracts in aimplaiogical menus to achieve the best possible results.
Horizon plus is delivered with a frame with rotating holders for 35 mm, 6 Cm × 6 cm and 4" × 5" films. Optional holders are available for batch scanning, uncut 35 mm strips and framed 35 mm slides.
Technological development is only of interest when the final product remains affordable. Horizon plus adds features across the board. Top performance in terms of cost, productivity, quality and flexibility make Horizon plus an ideal scanner for the price-conscious profession.
Arcus II
Arcus II dominates the A4+ desktop color scanner market. Successor to the awardwinning Arcus family, it features 36-bit pixel depth, a true density range of 3.0 D, resolution up to 2400 ppi for continuous tone pictures and an astounding 3600 ppi for line art. Clearly this is the desktop professional.
A transparency scanning unit is built into every Arcus II, taking full advantage of the impressive CCD technology, which is capable of registering 68 billion colors; No details are able to hide in even the darkest shadow areas.
Such an impressive range of leatures and additional bundled software might appear to be outside your budget. You will be surprised to find that the cost of professional -quality scanner is really” desktop”.
Duo Scan New
- Flatbed and slide tray-twice the functions. Not the cost
- Twine Plate Scanning Technology
- One-pass 36 bit color scanner
- 2000 ×1000 dpi-optical resolution
- Mac/PC compatible.
A New Large Format Imagesetter From Scangraphic
The most obvious effects of the continuous change in the printing industry are shown in the pre-press area. Digital work procedures become increasingly accepted and demand a consistent realisation of the companies regarding the input and output of digital jobs. Highest productivity and high throughout with simultaneous rationalisation of complex and manual work procedures determine the work process of modern and future oriented pre press companies. However, print house which in the past years were often only specialised in montage, copy and print, now also require an increased supply of modem imaging systems to achieve a more efficient work flow. Because instead of film, digital data is increasingly supplied -also to print houses, which therefore begin to invest in pre-press equipment again.
High demands on imaging systems
High performance, throughput, quality, precision and flexibility are the increasing demands placed on today’s imaging systems. These are the criteria which determine the economic viability of such systems.
The scangraphic family of drum imagesetters, first introduced to the market in 1966, has always possessed these characteristics, thus ensuring productivity and quality for typesetting and reproduction tasks. The new Scantext Apollo laser imagesetter is also based on the tried and trusted internal-drum technology onto stationary material, a technology which scangraphic established for the Post script output, thus setting a standard which has become world-wide for colour imagesetters.
The Principle of exposing images onto stationary photographic material within a drum guarantees exceptional precision, register conformity and reproducibility, an extremely rapid and thus optimal dot structuring and overall conformity of dot density.
The geniality of this principle is as simple as it is effective. To deflect the heliumneon laser beam onto the photographic material in the drum, a rotating mirror is used to deflect the beam to every point at the same distance and at. the same angle. During this process, the material is not transported nor is the laser beam modulated, two factors which could lead to errors in the dimensional stability. Thus, it is the tried and trusted Scangraphic indrum principle which fulfils the high demands of a colour imagesetter. Then geometrical accuracy and high reproducibility are the indispensable characteristics of the exposure of colour separation.
Continuous Progress in quality....
On the grounds of its comprehensive experience in the manufacture of drum imagesetters and vivid exchange with its customers, seangraphic has always continued to improve performance and quality of its imagesetters. The scantext Apollo thus now offers six different exposure resolutions with which the spot size can be varied between 8 and 22 my. These resolutions of 10 1 6,1270,1905,2540.38 1 0 and 5080 dpi and the variable spot size are the guarantee for optimum recording quality and the very best reproduction of the entire tonal value scale in black and white, colour and the frequency modulated scantext High Fidelity screening process. This high quality, however, also profits fonts, including those with the finest serifs, graphic elements with hairlines as well as negative, text and graphic elements.
During the construction of the new imagesetter, the main goal was to establish a balance between recorder speed and performance and to also ensure the highest throught put from the creation of a complete sheet to the final exposure. The overall consept of scantest Workstation and imaging system likes into account that tje capability of one component may not be blocked by another.
The main objective here was to reduce the total output time for a typical Al color
Sheet (eight A4 pages) to approximately four minutes, which corresponds to a maximum exposure time of less than one minute per color separation, and all this at a resolution of 1000 lines/cm or 2540 dpi. The typical recorder speed is 145 seconds at 1270 dpi for the full imaging format of 1072 × 770 mm. At the highest resolution, this results in an exposure performance of 56 seconds per A4 page.
On the one hand this does, of course, require enormous RIP performance such as that offered by scangraphic’s current Raster image processor, the scantext Prestoa software RIP developed on the principle of the Adobe CPSI and furnished with Pixel Burst hardware accelerator.
On the other hand, however, an output engine is required which can transpose the high RIP performance of the Presto into exposed film.
The scan text Apollo drum imagesetter, built to leading edge design specifications, fulfils these demands with the highest precision and at the highest speed. In combination with the new scantext combo RIP concept this has been achieved in a completely new way. All data which is made available for the generation of fully imposed sheet exposure is first transferred to the scantext combo workstation, which is a combination of server, imposition station and software RIP on one platform. The data is imposed and then calculated on the combo hardware. The Special feature of the scantext combo work flow is the ability to generate the high-resolution bitmaps required for the exposure in the background, and to thus minimize the time previously caused by the RIP process. Scantext Apollo exposes the complete sheet at its writing speed, as no further calculation times are needed for the postscript generation.
To cater for the increasing demand for imposed exposure, scangraphic has constructed a new drum designer the Scantext Apollo which features an extended circumference. This enables the Apollo to process jobs with a maximum hight of 770 mm. The 770 mm corresponds to an effective drum area of 85 degrees.
The exposable format was conceived on the basis of the facility to e xpose eight impsoed A4 page including all additional elements such as register marks and cut marks. The exposure format of 1072 × 770 mm fulfils these requirements and covers the Af oversize format. This means that an Al poster in oversize format, four A3 jobs, eight A4 pages or 16 AS pages car all be exposed on a single film.
The scantext Apollo is capable of processing different types of material (film or polyester plate) which are stored in exchangeable supply cassettes and allow the imagesetter to be rapidly adopted to the various fon-nats without any complicated mechanical adjustments being made.
Photographic material can be selected in any intervals and in width between 460 and 1082 mm. According to these material widths, scantext Apollo allows the application of various imaging formats and the use of polyester plates that conform to most popular printing plates.
Punch systems compatible to printing presses up to Al oversize
The scantext Apollo is equipped with a punch system that supports the Bacher 2000 or stoesser film register. The new feature of centered material feed allows centered register punching of film or polyester plates for all printing formats within the range of 460 up to 1082 mm punch side width.
By using the integral punch system, the user can copy directly form the exposed film to the printing plate without having to carry out time consuming work of remounting the exposed film for the subsequent copy process to the plate, or repunching.
The laser system of the scantext Apollo is based on the tried and trusted heliumneon laser which is already in use on other scantext laser imagesetters. The use of a helium-neon allows the application of cost -effecfive, standard film material. In comparison with laser diodes, helium-neon gas lasers are characterized by a better consistency of intensity anO considerably enhanced dot sharpness. The latter is becoming increasingly important for output quality in connection with frequency modulated screening techniques, and in particular for the application of scantext High Fidelity screening.
The high rotational speed of the mirror drives required for high exposure speeds placed extreme demands on the mirrors themselves. They must be light, stable, and must retain their optical characteristics even at high speed. With an eye on future developments, scangraphic has departed from the conventional all-metal mirrors as these are simply too heavy. The use of beryllium, on the other hand, is extremely hazardous due to the high toxicity (beryllium oxide). Instead, a solid glass model of scangraphic’s own design was used with the mirror surface composed of vacuum metalized aluminium with a special optical coating and protective covering.
RIP and RIP Interface
The performance of the scantext Apollo imagesetter is considerably influenced by the high mechanical speeds, the resolutions and the raster image processor, for these reasons, Scangraphic offers exclusively external software RIPS for the Apollo. The most powerful software RIP, scantext presto, is based on the adobe CPSI concept which enables interpretation of post script data on a software basis and uses a computer running on a standard platform (Spare technology). A special ASIC, the pixel Burst accelerator board, is utilized to accelerate the process of pixel calculation.
The scantext presto covers the entire spectrum of applications used in modem publishing systems. It can process all Level I and Level 2 Post script jobs and in addition to the original type I fonts contained in the scantext Digital type collection, can also process all original Type I forts irrespective of the manufacturer coupled with the high performance of the scantext Apollo, this facility to utilize toutilize proprietary DTP programs and fonts gives the user decisive advantages in speed and system independence.
The scantext Apollo is equipped with two RIP interfaces as standard the Li2/Li5 interface and the FPI fast Pixel Interface, the scangraphic standard for control of scantext imagesetters. The Li2/Li5 interface enables the connection of the scantext presto and Scantext Rip Express. For connection of the Rip Express, the Laser Bus interface is required as an option. All of the recent RIPS from scangraphic support the fast FPI which allows a pixel clock rate of upto 125 MHz.
Technology aspects
For the electronic control elements of the Apollo imagesetter , scangraphic has departed from the now outdated VME bus, for reasons of better serviceability, flexibility and the promotion of EMV, scangraphic has implemented the principle of distributed intelligence on the the basis of CAN bus technology ( Controller Area Network). The individual components can be tested independently of each other and the main system, thus simplifying service aspects. Of the nine components contained in the electronic systems of Apollo, five are absolutely identical, achieving rationalisation of spare part management, in addition, this concept enables remote diagnostics of the imagesettter, which involves considerable saving in time and costs.
Every scantext Apollo is equipped with an internal data bank containing parameters relevant to the materials and which can be expanded and modified at any time. If a new material for printing plates is utilized which, due to its mechanical stability requires other speeds, for the transportation of the materials to and from the drum, the parameters for this material can then be defined by the user and entered into the data bank.
The scantext Apollo embodies scangraphic’s experience in the development of hightech products for the graphics industry. In combinationwith the scantext combo workstation, the output on film or polyester plate meets the demands of a modem and efficient work flow. Scantext Apollo combine the tried and tested scantext Apollo corfibines the tried and tested Scantext in-drum principle with state-of-the art mechanical and electronic technologies.
The Scantext Apollo is thus the ideal output medium for fully imposed sheet assemblies, and offers completely new perspectives for the digital work flow in the pre-press industry.
Scantext combo: optimum job Management through combination of Workflows
Prior to the introduction of the Scantext Large imagesetter, Scangraphic had defined the basic principles for a new RIP concept. This concept is based on the understanding that recorder speed and RIP have to be adjusted such that neither component in the production chain has to wait for the other. As the slowest element of the chain determines the throughput, the speed of both RIP and imagesetter had to be adjusted with each other. This concept is currently successfully applied with the scantext Presto software RIP in combination with the scantext Apollo and Scantext Largo imagesetters.
Combo combines several work procedures
Scangraphic has now added a unique and productive feature to this RIP philosophy -simultaneous imposition of complete sheet assemblies and ripping on one work-station prior to the imaging process. This extended concept, called scantext combo, runs on a Unix workstation with spare technology, and combines server functions, imposition software and software RIP in an extremely economical way-all on one plateform.
Data output is rationalised considerably, and complex calculation procedures are reduced to a minimum bits is an important requirement for efficient and highly productive application of large format imagesetters.
The combo Philosophy
Scantext combo may be explained very easily by a Practical example very easily by a Practical example during the production of printed matter such as magazines and periodicals, the work flow may be interrupted due to missing pages or because of last minute correction of a single page. Why should the Production have to wait until the missing pages are available?
The philosophy behind scantext combo is to take into account these missing pages in the layout sheet of the imposition software, but they are not relevant for the continuing production process. All available pages of the job can be imposed and ripped for the final exposure. The RIP renders the data as bitmaps in the final imagesetter resolution and saves them temporarily on the system. When the missing pages are available, they will be ripped and included into the complete job.
The whole job, stored as bitimaps on the system, is then sent to the imagesetter. There is a considerable saving in time, because the imagesetter only outputs the data as precalculated bitmaps. The RIP process during exposure is therefore unnecessary.
Imposing with scantext
Production in the pre-press area demands imposed sheet assemblies including au control elements such as cutmarks and colour control strips. The last step prior to the plate copy, the generation of the monttage films, is not to be made manually at the light table but electronically at the monitor using an imposition program. PostScript data form applications such as page Maker, Quark X-Press and Freehand are entered into the program, analysed and automatically checked for completeness by the program. The previews of the pages are included into the imposition layout, and the complete imposed sheet is stored for the exposure. For the assembly display on the monitor, new resolution previews with a resolution of 72 dpi are generated by the scantext RIP.
Scantext combo uses the advantage of the imposition software and includes them in the combined concept of imposing and ripping. Combo’s special feature is the ability to generate the high resolution bitmaps exposure in the back ground, and to thus minimise the time by the RIP process.
Preparation for the Exposure with scantext combo
The sheet assembly is carried out at- the imposition terminal by using the lowers file generated by the RIP. An automated work step of scantext combo-program, the bitmap control, checks whether the high-resolution bitmaps needed for the exposure are already available or whether these data were still have to be calculated by the RIP. Once all data (bitmaps of the page) is submitted, scantext combo starts the actual output process. The complete sheet can now be output at the writing speec or the imagesetter, without additional RIP times.
Imagesetters are for imaging
With this technique, Scangraphic has optimized the RIP Process to such a degree that the customer is unaware of the lengthy Processing time of several colour Pages. 7ber RIP process is carried out as a background operation so that the imagesetter’only has to image.
This procedure is especially suited for large formes or multiple copy exposures output on scantext Othello imagesetters (eight A4 pages each) for output of fully imposed sheet assemblies.
DIGITAL COLOUR PRESSES & COMPUTER TO PRESS
There is no universally accepted definition of the term “digital printing”. Probably this is why it is a subject of discussion. In fact there are two basically different points of view are those who in the computer Industry and another the printing industry.
For the computer Industry, every printout of data on paper is an example of digital printing, whether it is in black and white or colour. As result the digital printout machine is known as “printer” which to the prirting industry means the technician w o runs a press.
Plateless
The printing industry speaks of digital printing when the computer is connected to the printing press and the digital data produce. The printing forme directly in the press. This means plateless information transfer or non impact printing.
How did it Start- Heidelberg unveiled the world’s first digital printing machine at Print 91 exhibition in Chicago in the form of the GTO-DI, thereby initiating a new direction to the development of printing machines and the printing industry.
At Ipex 93 in U.K. two innovative machines were introduced but only could print up to A3 size and did not become available until 1994. They are the E-print 1000 from the Israeli firm Indigo and the Chromapress from the Gerinan-Beigian firm Afgo-Gevaert. The latter machine has been developed by Xeikon, a firm established by Agfa-gevaert Xei ton’s own channels of distribution under the name of DCP-1 Digital Colour Press).
The computer industry has an urgent need of digital printing for the continuation of its growth. To enhance the value of the computer and promote its sales it must be possible to print out the colour screen display, including pictures, cheaply & rapidly on paper.
At the 1992 Seybold congress in San Francisco, the then president of Apple Computer, John Scultey pointed out that conventional offset printing was unacceptably costly affair for the short runs required by the Computer Industry. He almost challenged the entire suppliers of printing machinery to develop further a means of printing off colour pages at much lower cost, other wise the computer industry would have to develop such devices for. itself.
Digital Printing for the Printing Industry
As a matter of fact the whole subject of digital printing runs counter to the interest of the progressional printer. The question is why should user spend more money to buy an additional machine simply to sell shorter runs ? Should he/she split, up his/her long runs into a number of short ones’! His/her customers would gain the advantages of reduced stock and rapid up dating. But again would they pay extra for these ?
Would customer be prepared to pay an express charge for same day delivery of a few hundred sheets, as it is acceptable in the photo business ?
Naturally there are some good reason for adding a digital printing service to conventional printing.
Digital-printed jobs can be delivered more quickly, short runs can be produced more cheaply.
Digital Printing for pre-press companies
Prepress services have far more reasons than printing companies to take up digital printing. They control the production of data and the process. They already have data. With digital printing, they can extend their services and increase their turnover. Production can be ultra-rapid if one makes use of the synergies of the chain of digital data.
A page can be created, imaged and printed in fifteen minutes from the digital camera and text entry to the finished print.
These possibilities are, of course, dependent on the purchase of a digital printing machine plus finishing equipment, which represents a high investment.
Digital Print
To day printing technology has become an industrial process. With standardization and automation, prices have come under pressure. Anyone who wants to make money out of print must lower his costs, both on press and pre-press stage. From the cost point of view it makes little difference if savings are obtained in the manufacturing process or new markets opened up by digital printing.
Several other possibilities are open to the printer such as
- automatic imposition
- digital platemaking
- automatic platechangc
But in any discussion of digital printing it should be made clear within whether one in speaking of small A3, medium A2 to Ai or large formats, because the Price/performance ratio is different in each case. It is known that digital printing in A3 size from single copy to long run, is already available in the International market with a variety of machines.
Gravure periodical printers, who engrave cylinders directly from digital data, can witness that the disproportional organizational effort involved, could hardly be justified in offset, with its comparatively single platemaking procedures. Rapid automatic plate change, on the other hand, will certainly reduce offset production costs.
For medium size, whether suitable digital printing machines will be an offer, or whether the combination of computer-to-plate and quick, automatic plate change will bring the required cost reduction for cheap, short colour runs.
It we look at from the offset printer’s point of view, a reasonable requirement would be the hybrid digital printing machine, capable not only of imaging plates produced off-line, whether by conventional or digital means.
Making digital plate production cheaper
Printers and pre-press People will have to Consider whether digital plate imaging in the printing machine kes economically viable or not.
It is reasonable requirement to be able to carry Out plate exposure within the imagesetter, which could then Optionally expose either to film or to a aluminium plate.
For longer runs, electrostatic systems are currently the most successful technologies with speeds that approach those of conventional lithographic printing. In future it is possible that ink jet may emerge as the most viable digital Printing technology, but at present the difficulty in achieving acceptable resolution at high Production speeds excludes Inkjet from colour printing at speed.
In order to compete with conventional printing presses, digital colour printers combine some features of conventional press configuration with innovative imaging methods in a hybrid design, that resembles neither the same-scale office printer nor the conventional production press.
Since high production volumes are essential to recover the relative! high capital costs of digital presses, it is importent for uselessrs to consider work flow management, including the preparation of pages.
In some cases, the press may be unable to handle the amount of data needed to change the whole image an each impression and only, a part of the page can be variable on each copy.
Digital colour presses are faster to set up the than conventional presses, since there is no need to adjust position or inking levels. Proofing is done by print run. The proof, and exact fasimile of the production run is in effect a production press proof.
The drum technolgy used in electrostatice digital printers in essentially the same as that used in laser printer and photocopiers and it must be replaced regularly. On a high volume multicolor printing systems annual maintenance costs can be very high.
Xeikon DCP-i-This is developed by Xeikon of Belgium, use dry electrophotography and employs a multi process approach to enable fully variable data to be processed. It is reel-fed printing to 2000 pages per hour, The maximum sheet size is 12 x 17 inch (307 x 438 mm).
Eight seprate printing, units print cyan, magenta, yellow and black on each side of the palper. The imaging heads, operate resolution of 600 dpi, but are able vary the amount of charge imported to the drum by the LEO spot. The greater the charge, the more toner and thus a variable spot density, can be achieved up to Offset.
Barco and Agfa developed front ends of the Xeikon engine. The Agfa Chromapress sophisticated workfow planing functions, together automatic imposition.
Indigo E-Print:- The indigo E-Print has only one printing unit, but by feeding the sheet back through after each consecutive pass, it can print upto six Colours On each side. Liquid electrophotography allows the E-Print to- use pigment particles of 1-2 microns in size, giving improved resolution with smoother solids and better highlight detail in compan’son with dry electrophotography. The liquid ink polymerizes instantly on contact with the paper, printing a very sharp image with no physical dot gain but optical dot gain is still present.
THE DIGITAL OFFSET COLOR REVOLUTION E-PRINT 1000
Affordable short-run colour printing is possible for the first time with E-Print 1000, the world’s first Digital Offset Color press.
Digital Offset Colour combines the professional quality and high throughput of offset printing with the flexibility and ease of use of electronic printing. Indigo’s unique Electro Ink technology, enables brilliant magazine-quality glossy colour images. A fully electronic imaging process produces just-in-time, on-demand printing without films, plates, proofs or make-ready.
E-Print 1000 brings the printing industry to the best of both worlds.
Printing directly from digital data, accepting industry standard formats like Postscript and Scrtex, E-Print 1000 can operate as a stand-alone unit or network with pre-press and desktop publishing systems.
E-Print 1000 accepts a broad range of coated paper stocks as well as uncoated paper up to 320 × 464 mm /1 2" x 18" size. At a process speed of 120 feet per minute, it can print 2000 fullcolor (or 8000 single color) lettersize images (two-up) per hour. With a standard printing resolution of 800 dpi, E-Print’s proprietary image enhancement technology achieves outstanding, crisp, brilliant images, both for text and color graphics. The standard configuration is capable of printing In full colour, using four process color inks. An optional feature is six colour printing. This enable the user to add special purpose inks or coatings.
E-Print 1000: Combining Simplicity with Power
Printing with E-Print 1000 does not involve the tedious, complicated and expensive operations required by conventional color printing. The entire process is automatic
- E-Print receives the input data.
- E-Print processes the data for printing.
- The job is printed
It’s that simple!
Economic Advantages
E-Print 1000 eliminates the expensive materials, the time-consuming processes, and the skilled labor requirements associated with conventional offset.
No Films or plates: Electronic data is received directly from the publishing system.
No proofing : On- demand single prints replace proofs, instantly-on the-final paper, using the final inks.
No press make-ready: Perfect registration is assured and colour balance is automatic.
No expert operators required: Quality is assured electronically, without dependence on press operator skills.
Because E-Print 1000 is so easy to set up, and easy to use, quality color printing is more economical than ever-even for very short runs!
Additional Options
Beyond saving time, materials, and money, E-print 1000 offers new printing capabilities never before possible.
Electronic Collation: With no plates required images can be modified electronically-at full printing speed, even from page to page. This option enable even complex publicators to be printed in their entirety, with each page in its correct sequence.
Automatic Duplex Printing (Perfecting): Each page can be automatically printed on both sides. This option, together with electronic collation, means that an entire multi-page document can be printed-ready for finish-ing-fulfy automatically.
Booklet Maker (Automatic Booklet Making): This automatic finishing option enables the production of fully-finished booklets-folded and stapled-with no manual intervention.
Personalization: One-of-a-kind full colour documents-with variable text and images on each page-can he created in real-time for.targeted direct marketing driven by database profiles. This option opens up new markets for short-run printing, facilitating on-demand colour, economical distributed printing, and even individually personalized publications. By combining the power of Digital Offset Colour with electronic collation, automatic duplexing (perfecting) and automatic finishing, the E-Print 1000 can deliver fully-finished printed products-just-in-time. From pre-press to finished product, at the touch of a button on demand! This makes even the shortest runs economical, for the first time.
Many colour printing jobs such as product brochures and promotional materials, are now printed on the E-Print 1000 as multiple, on-demand short-run jobs. By printing on demand or “just in time jobs on the Indigo E-Print 10.00, you can make last minute changes in order to update, modify or customize the finished product.
Printing speed is 8000 pages per hour for one colour, but every subsequent colour halves output speed. A four-colour duplex job is outpt at a speed of 500 copies per hour. Print resolution is 800 dpi, and the resolution enhancement technology used make the print appearance similar to conventional offset at a 150-lpi screen ruling.
A 640-MB buffer stores upto 100 compressed and rasterzed pages at a time. For to very it for each copy. However, it can rasterize the variable data and combine it with the constant page elements at the full production speed.
The single-unit design calls for the ink to be removed from the printing blanket after each revolution. To achieve this the ink has to be formulated with relatively low adhesion, which also means that as a result. It can be rubbed off some printing papers.
Digital colour printing technologies will continue to develop. Some will represent radical departures. Some will be evolutionary changes to current systems and others will be novel hybrids of existing and new technologies.
Digital printing
Short- run colour printing, using technologies and devices designed to replicate proms colour work at speeds of at least 2000 A4 pages per hour, or 900 pages printed on both sides. The devices concerned code (usually postscript), interpret the data in the form of a bitmap by way of a’ raster I image processor, expose this onto an intermediate carrier and finally replicate the result on paper or other substrate.
Major economies are promised by this all -digital procedure, which eliminates digital data and the printing process: not only film and plate materials but also imagesetters and chemical processors. Make ready times and start-up waste are reduced and almost instant register is achieved, all without the need for any traditional craft skills.
In addition to technical simplification digital printing offers publishers the advantages of “just -in-time” or” on-demand” production to meet the needs of reduced inventory and frequently changing content.
Two radical changes made possible by the digital printing methods are the reversal of the publishing procedure from “print and distribute “to” distribute and print” and the ability to change the image on each revolution of the press.
Distribution of digital data over a computer network enables the digital press to be regarded as a peripheral device for printing the quantity and version of the images required at any remote site, thereby practically eliminating the need to transport any finished print work.
Variable data printing not only allows the output to be localized or personalized but opens up the possibility of printing a series of pages in the correct reading sequence so that finished multi-page documents emerge from the press, other ingenious uses of the new facility could include interrupting the press run for the production of an urgent proof of another job, or indeed a complete rush job “on the fly” without any waste of materials.
Digital printing as the final step in the evolution of print production form a craftbased to a technology-based business. There is no technical reason why it should not be undertaken by publishers, designers, corporate offices and other traditional clients of the printing industry. The inhibiting factor is the high capital cost of the machinery. Which ranges from US $ 200000 to $.500000. The consumable needed for digital printing are also 4 major cost factor, especially the tonner, which can cost forty times as much for a process color set as the equivalent quantity of litho inks.
Other major disadvantages of digital printing as comparedwith modern offset-litho are (1) the speed of output, which is anything form three to ten times slower, (2) the maximum sheet size of SRA3 or a little larger, and (3) the quality of the colour print, which although impressive is undoubtedly inferior to the best that an offset-litho press can produce.
To increase the speed of output and maximum sheet sizes of digital presses would call for a signifcant increase in data transfer speeds, which at present do not exceed 600 MBs,
Market forces
Two factors favourable to the rise of digital colour printing the growing demand for colour in all communications media and an increasing intrerest in short runs, tending towards” print on demand”. These factors have stimulated the development and installation of machines such as the Agfa Chromapress, Xeikon DCP-1 and the Indigo E-Print 1000. At the same time these machines, however impressive their perfomance may be, do not automatically qualify for a significant slice of the printing market. Runs from 50 to 1000 copies, which would seem to be their natural target, are under fierce competition from below i.e. from better, cheaper and faster colour copiers, and above, i.e. offset litho presses with automatic features such as wash-up plate change and computerized press settings.
In consequence, Agfa and the other suppliers are now giving greater importance to the unique selling proposition of variable data printing. Which digital imaging offset presses cannot offer. The tremendous success of Heidelberg’s new Quickmaster Dl 46-4 owing to its rapid imaging, speed and print quality , does not alter the fact that the plates can be imaged and used only once the Quickmaster Dl essentially embodies computer-to-plate philosophies, but applied on-board to a printing press.” Its technology is therefore quite different from that of the true digital press, which as already mentioned is basically a computer peripheral.
The market for digital colour printing will comprise average run lengths and order values much smaller than those in other sectors of the industry. This means that far more jobs will have to be found to keep these new machines busy and profitable. Which implies a completely new approach to print selling. Digital press users will also need to have an associated pre-press system in order to meet the need for an all -digital workflow.
Available equipment
A detailed description of five s%lstems for short-run colour printing : Agfa Chromapress
Xeikon DCP-1, India E-Print 1000. Scitex spontane and Heideioerg Quickmaster Dl
46-4. The main specifications are summarized in the Table which accompanies complied by Lawrence Wallis.
All except the dry-offset quick master are based on the electrophotographic process, which allows for variable data printing.
The xeikon engine constitutes the output portion of the Barco Digipress and the IBM Digital colour printer, in addition to the Chromapress and xeikon’s own machine. Differences between the systems relate to front -end control, data, management and image processing equipment.
Xeikon -based machines are web-fed and equipped with a set of four process-colour print heads on each side of the web: a configuration most effective when producing two-side printed sheets. Work of this kind can be produced at 2100 A3 pages per hour, which is about four times faster than the equivalent production on the Indigo print. On single-sided printing the output is more equal, with 1050 A3 pp/h from the Xeikon engine and 1000 from the Indigo. (For A4 output, simple double all figures.)
Speed difference
E-print 1000 is one of several Indigo products, including the omnius for packaging, labels and decorating and the Mobius for publishing applications. It is based on the design of the Ryobi small offset press, as can be seen from the blanket and impression cylinders. There is also the less familiar electrophotographic cylinder fitted with a photo imaging plate (PIP). With a single, sheetfed printing unit, four cycles of the machine are required for single-sided process colour printing and eight cycles for perfecting the same-which accounts for the relatively low output compared with the web-fed Xeikon engine.
Indigo’s patented Electro Ink is a vital element in the E-print process. When transferred from the photoconductive cylinder to the blanket by pressure, Electroinics are slightly heated and become tacky, but when they are offset to the paperthey peel away completely from the blanket and instantly harden, paper sheets from 60 to 250,gsm can be handled without difficulty.
Scitex introduced its spontance digital printing machine at a price of approximately US $ 220000. Spontane undercuts Indigo units by some 50 per cent and xeikon-based systems by about 40 percent. Output is 450 perfected A3 pages per hour. The machine consists of a Fuji-xerox electrophotographic print engine driven by a scitex RIP and data control system, with a print head for each process colour. Speed is achieved at some expense of resolution, which is 400 dots per inch as compared with the 600 of xeikon and the 800 of Indigo. On the other hand, a spontane pixel has a variable density of up to 256 levels, while an Indigo pixel has two and a xeikon pixel 64 levels. Paper substances from 64 to 220 gsm are accepted by trays holding 250 and 1000 sheets and automatic two-sided printing is built into the equipment.
Digital but not variable data
Heidelberg’s quickmaster is the successor to the same company’s GTO-DI but retains the proven Presstek plate technology. It offers more streamlined operation than the previous machine, with automatic plate cleaning after imaging and automatic blanket washing at the end of a run.
Change -over time between jobs has been greatly reduced by the introduction of rolls of polyster plate material, housed with in the printing cylinder and rewound on another interior spindle after use. thus never being cut. One plate roll accommodates 35 jobs.
Bearing in mind that it does not accept variable data, the Heidelberg machine is superior in all other respects: maximum sheet size 460 x 340 mm, runs up to 20.000 impressions per plate, speeds 3500 to 10,000 A3 sheets per hour and above all offsetlitho quality. The manufacturers describes the quickimaster as being suitable for runs from 200 to 5000 copies. The price of the machine is naturally higher, being quoted at US $ 500,000 in the UK, or about 12 to 36 percent more than a digital press accepting variable data.
Digital printing
Latest of the high-speed non-impact printers from the French company Nipson Printing system (a member of the Bull group), Nipson 7000 is based on a magneto-graphic motor printing at 60 metres/min with a resolution of 240 dpi. The manufacturer promises an improvement to 480 dpi in 1996.
Magneto-graphic technology. First developed by the Bull -roup in the early 1980s, is based on an array of writing heads which compose, dot by dot, a latent image on a metallic drum. The image is revealed by contact with particles of magnetic ink (also a Bull product) and is then transferred to paper and fixed.
With its high speed of 60 mmin (compared with the 45 mmin of the fastest laser printers), Nipson 7000 accepts standard paper reels of 520 mm width to Orint up to a width of 45 mm. This width allows for the personalization! of large forms used in direct mail campaigns and also the printing of two A4 portrait formats side by side for subsequent splitting and finishing on standard A4 post.-press lines.
Nipson 7000 also benefits from a new technology of fixing the toner by flash at 50 C, a much lower temprature than the usual 160 to 180 C. This eliminates the problem of deformation by heat and extends the range of acceptability of fragile materials and those subject to complex conversion processes, for example labels, window envelopes. Pre-glued envelopes, self-copying papers, plastic materials and so on.
A unique optional function, to be released in 1996; is the single Engine Duplex (SED) features for the perfecting of A4 pages at 400 images a minute, also suitable for oneside printing in double format.
Already available for perfecting is the use of two synchronized printers in line, producing 800 images a minute. Each printer can also be used separately for one-side printing.
The printing system has as extensive range of possible connections, up to three at a time, with data processing systems from IBM, Token Ring, Ethernet, Data products , etc. As an autonomous station it can readmagnetic tapes, enhance the raw data and control the print output. It can also be easily integrated irto any pre-press or post-press production line.
Feed is by reel unwinder or from a pile of up to 10,000 sheets. In-line delivery possibilities include rewinding sheet splicing, folding and cutting stacking with conveyor belt.
While Nipson 7000 can produce complete monochrome documents in black, red or sepia, its main application will be the printing of variable data, including bar codes and numbering, on preprinted documents such as continuous forms, direct mail and labels.
It is also the printing element in the new Nipson Vary book press for the production of monochrome books on demand.
Running costs are low at 250 FF (about USD 50) for I kg of toner enough for 40,000 A4 pages, but the basic price of the full width printer with software and paper feed and delivery components is high at 1.5 million FF or about USD 300,000.
Finishing
The automation of bindery processes and functions is advancing rapidly. Pre-setting of machines is becoming available for the mainly European equipment ranges from ferag, Kolbus. Mueller Martini and Polar, to name but a few. Civiemme, Ferag, Mueller martini and Rima presented complete mailroom automation systems, Baldwin offer systems solutions for mailroom handing, print finishing and value-added production processes. Other manufactures with this “value added approach” are Gaemmerler and Hunkeler.
Quad-Tech FCS is a print finishing management system especially suited for demographic (split) edition work. Up to 1000 different personalized targeted inserts or imprinting (including inkjet printing) can be input and controlled electronically, This immense variety of demographic possibilities is not unusual in North America. One farming weekly offers advertisers 1000 demographic “splits” via the bindery.
Bourg and Duplo have teamed up with digital pressmakers to offer integrated print and finishing solutions.
Bobst, having just introduced the Masterflex 160-Amatic multi-colour flexo system, presented the medium-format SP-6 BM foil embossing and diecutting machine for primarily short run work. The machine is touch screen operated and also allows production of holograms at a sped of up to 000 sph from the reel. Formats are up to 560x60 mm. The new Autoplate SP 104-ER offers automatic blanking. Up to 8000 sph to a max. Width of 1040 mm in weights from 80-2000 gsm (or corrugated board up to 4 mm thick) can be handled.
Technology Trends Pressroom
Komari have made a real comeback in North America in the sheetfed market. A 10-unit press has gone of Jefferson Smurfit at Greensboro NC. The Luhrone 40 has eight printing units and two coating towers, plus extended delivery. Consolidated press is installing an eight-unit (4+4) perfector in Chicago II. Color graphics in California is installing six and eight-colour Lithrone 40s for waterless offset. A sixth Komori machine, the world’s first Lithrone 844 RP, is being installed by H]M Smyth in St. Paul MN. The machine prints labels with two-colour perfecting.
Speedmaster CDs and the new SP range from Heidelberg, but also the roland on have gained exceptional sales successes in North America. Smaller A3 formats are gaining increasing colour printing market share. Speedmaster 54 and Roland 300 machines attracted large crowds during print demonstrations. Sakurai (Oliver) and other Japanese manufacturers are following the international trend to up to six colour configurations for smaller formats. Sakurai also introduced integrated CTP for their machines.
King Press and Tensor Group report excellent export results for their single width newspaper and hook presses. King press have also created a sizeable quality heatset colour market for their presses. Tensor have more than 180 press units operating in Scandinavia and Italy.
Two British manufacturer following the earlier success of BakerPerkins (now Rockwell Graphic Systems)-have gained excellent markets in North America: strachan & Henshaw, who claim that the lion’s share of US pocket book in produced on their machines, and Timsons. S&H are shipping a variquick to king printing in Boston MA
Where the machine system’s interchangeable printing cassettes (with off-press unit make ready) will be used. Timsons, in cooperation with Kolbus, demonstrated integrated printing and binding on the T 32 press Rockwell Graphic systems presented the BPG-25 and the World 16 E 16-page web offset press ranges.
All over the world, sophisticated sheetfed and web offset presses are operating which were installed before electronic ink setting and adjustment became standard. Many of these presses have been and are being retrofitted by US supplier perretta who report installations in North and South America, Southeast Asia, South Africa and Ofcourse Europe. The system 21 00 offers ink setting and adjustment, as well as management control.
Colour master is Rockwell’s ink and management control system for web presses that reads both proof and press copies. Re -setting and adjustment are fully automatic. QuadTech CMS -together with Light sources Colour torn offer the CMS system for automatic ink setting and adjustment based on density measurement.
Computer-to-plate step by step
Today many printers are investigating the possibility to expand their pre-press departments to handle digital dita. The reason for this being the dramatic increase in jobs received in digital form
This increase is specially noticeable for commercial, magazine and catalogue printers, where the amount of digital pages have generally been doubled during the last year.
The book and directory printers have had the access to digital data for several years, but over the last two years the need for handling digital data has increased, mainly due to financial and efficiency demands.
The packaging industry will probably be the next market segment to be influenced by the trend of digitatisatioii.
Production methods
What production models are then available for digital data handling today? There are three different methods, namely
- Hybrid system
- Computer to large film.
- Computer to plate
These techniques as well as their advantages and disadvantages will be described below.
Hybrid system
Hybrid system means a production environment that can handle both convention film originals and digital data. Although many companies will assembly pages in computers in the 1990’s, the conventional method of using film will not be neglected, especially for magazine and commercial products. Ads arc received from outside as films or are to be reused From earlier issues, these ads can certainly be converted into digital form by scanning the images. The printer, however, does not have a high quality scanner the graphic result is often not accepted by the advertiser.
This system creates the flexibility to handle different types of media and the printer can, at the same time, utilize the products already has in the production. Another important benefit with this system is that it is not necessary to change the production organization radically in order to begin production with digital data.
What is the Hybrid system?
The main components in this system are an imagesetter which is equipped with are gister system, a film handling system for rational handling of conventional films and a step-and-repeat or imposition machine for plate making. All components are controlled by plate planner, an impo-sition program which handles imposition of digital pages in an imagesetter, controls the flow of films via a-film checking system and controls the plate making.
The production flow through the hybrid system occures in the following.manner; The digital pages ire exposed in imposition order with necessary register and press marks in the image setter. Postscript imagesetter is equipped with register and can expose up to 4 × A4 pages, controlled by the plate planner program. After processing, these pages are ready for plate making i.e. no further page preparation is necessary.
Ad pages and other pages which are available as film originals are register punched and/or assembled in a film handling system. This system mainly consists of a mounting table Autopunch for automatic register punching of the film originals and possibly a Dual Page system which converts the double page spread films from readers pairs into printers pairs.
All films are then loaded to Pre-load Cassettes and are controlled by the film Checking system to eliminate the risk of incorrectly imposed plates Finally the pre-load cassets are loaded in the imposition machine and the printing plates are exposed.
A more flexible and rational system for hybrid production is not available today.
All data in digital form
Before discussing the various computer-to-plate solutions, we shall examine how to successfully use this technique. There factors have to be attained to make a workingreality of CTP.
- All material must held in digital form in computers.
- Correct electronic proofing
A powerful computer network.
One very important reason for going directly to plate is that all data is available in digital form in the front end system. This is the first, and for many, the largest problem to overcome, when investigating the possibility to convert from conventional to digital production.
Book, manual and catalogue printers are the most successful users of modem CTP technology and the main reason for this is that one source creates the complete product and that there are usually no ads in these products.
Digital Proof
With all material held in the computer digital proofing is needed. For black and white products this is easy, because laser printers can produce satisfactory proofs. For spotcolour pages, a colour laser printer is also acceptable.
With four-colour pictures, everything becomes more complicated. Most companies will have to output four separation films and produce a conventional proof, even though the corrections are made afterwards in the computer.
Fully digital proofing is possible today, although expensive. A large company producing top-class colour work regularly on a three-shift basis may profit from a earn digital proofer, but smaller companies have to wait years for affordable versions.
Net-working
Scanned pictures, page layouts and text demand a lot of disk space. For efficient production, avoiding constant disk handling, a digital network is needed. Normally, dividing the production process into four sectors is recommended.
- Scanning
- Text entry
- Interactive make -up for individual pages
- Automatic imposition and job planning
When the scanner and text entry operators have finished their jobsthey store the material on the file server, where other operators can access it for page make-up,
Although modern networks are powerful, it is not practical to have more than 20 operators logged in at the same time on the same network. Even with 20 operators waiting time for data file transfer is often irritating. To build up an effective network is complicated, but a lot is happening in this area. Good, high speed and not too expensive solutions are already available and new techniuqes are constantly being developed to increase performance.
Impositions
When all pages are sorted in computers, the problem with digital proofs has been solved and the network is in place and running, one can start to look at imposition programs and imagesetters or platesetters.
There are different general imposition programs on the market. A unique user interface has been developed in the Plate Planner. One of the more intresting functions is that a sheet is folded on the computer screen as it was made by hand. With this technique important advantages are obtained in the next production step; pagination and calculation of shingling and creep. The program also handles the generation of bar codes which can be used for film or printing plate identification at a later stage in the production process.
Imagesetter and RIP
When evaluating different imagesetters it is very important to test that the registration accuracy is within specification, in other words that the product’s mechanical stability and repeatability is perfect. Furthermore, it is important that the RIP is powerful since it normally determines the productivity and is therefore an important part of the system.
A few years ago all RIPs were hardware units. For increased speed or functionality, new hardware had to be designed. Today. RIP is a software package loaded into a computer, i.e. the power of’the computer that determines output speed. It is very simple to upgrade the RIP to achieve higher performance and new functions with this design.
Platesetter
It is based on external drum technology and designed lor exposure of both printing plates and film material.
It can handle image formats of up to 16 A4 pages (max. size 1016 x 1270mm or 50 x 40"). This provides printers with the ability to impose plates and films electronically, which are large enough for most common press sizes-.
In this machine it will be possible to produce approx. 6 printing plates or films per hour unattended.
CTPor CTLF
If plates or films are to be exposed. it is mainly a question of printrun, production flexibility, last-minute changes, proofing method and accepting time for remaking printing plate. These questions are very important to be answered and dependent on the type of production and internal organization.
Laser plates
Hoechst and Dupont are the two plate suppliers, who, until today, have introduced laser plates with an AL-base, However, some of the other large plate suppliers are doing intensive research work on new type of laser plates, thus can expect to see other high quality, long-run plates for CTP systems.
QUALITY & PRODUCTIVITY
Introduction
Shows the process chain for the production of printed products. Starting from an original copy, via the prepress processes and colour separation techniques, etc., the printing plates are produced that are required for the printing process in the press. The press has to be supplied with additional materials, such as paper, ink, fountain solution. The printed paper becomes the final product via the finishing process (e.g. cutting, folding, stitching, binding wrapping).
The printing process itself is determined by the type of printing technique that is used, e.g. letterpress, lithography or offset, or gravure. The majority of printed products worldwide-more than 60%- is produced by the offset process, with gravure and letterpress having approximately equal shares. Printing can.be done on sheetfed or webfed presses. The quality, efficiency, and productivity of offset, are determined mainly by the press design, the process steps, as well as automation and measuring techniques and equipment. Quality and productivity are the main themes in the following. Production is carried out mostly on sheetfed offset presses. S” shows a four-colour press, with integrated coating unit, shows a web offset press such as is used for higher run lengths. In web offset, a continuous paper web is printed and usually transformed into the finished product, e.g. folded advertising brochures, in an in-line operation.
An overview of the influences on the production of printed products
The offset process
A typical original for colour printing is, for example, a photographic picture, which, with the aid of colour separating and scanner techniques, the selection of the colour separation for the cyan, magenta, yellow, and black inks used in offset is carried out, on which basis the corresponding printing plates are produced. These four colour separations are printed in sequence on the paper in the press via four different plates, thus producing the colour image.
Sheet-fed offset press. Four color with coating unit, model: specification 102 V+L Heidelbereger Druckmaschinen AG.
Web-offset press. Model: Web 16. Heidelberger Duckmaschinen A.G.
Shows the diagram of a four-colourpress built in accordance with the superior modular design. The paper to be printed is supplied to the first printing unit by the feeder, where the first colour separation is printed. The printed sheet is then transported via a cylinder system to the second printing unit, where the second colour is printed. Printing of the third and fourth colour is done in the same way, The finished sheet is subsequently forwarded to the pile in the delivery via the delivery system. The elastic, unstable sheet, in a typical size of about 70 cm x 100 cm, must be transferred with maximum precision from cylinder to cylinder at printing speeds up to about 13,000 revs./h, or3riVs respectively. Consequently, this makes very exacting demands on the mechanical design of the press, in order tp ensure the control of the “paper flow.”
Diagram of a Four colour Sheet-fed offset press. Model: Speedmaster 72.
Similar exacting demands are also made on the “ink flow”. A finely adjustable ink transfer to the plate is made possible by an optimized design of the inking system and dimensioning of the inking rollers-a typical required ink layer thickness on the plate is about 3 m, and this must be consistent across the entire plate surface (see Fig. 5. And Fig. 6).. The offset process is based on physical/chemical surface effects on a flat printing plate and, for the separation of the ink-carrying and ink-free parts of the print images, requires the preparation of the flat plate by the preparation with a very thin (about 2 m) consistent fountain solution film—such as is made possible by the today given modem film dampening systems.
In line coating unit with IR or UV drying in sheet-fed offsets model: Speedmaster CD.
Offset is an indirect printing process, i.e., the image of the plate is transferred firstly to a cylinder on which a rubber blanket is mounted, and only then to the sheet that ion cylinder. This is possible only by an optimal matching is transported by the impress teristics and the materials concerned : ink, dampening of the physical surface characteristics and the materials concerned : ink damping solution, plate materials (e.g. diazo varnish and aluminium), as well as the rubber blanket and paper.
Printing quality
The quality of the multi-colour printed image is determined mostly by resolution, inking, and register. It is the screening of the colour separations that mainly defines the resolution. Today, printing is usually done with a resolution of 60 lines/cm, i.e., the interval between screen dots is 160 m. The quality of the press also permits the printing of considerably finer screens, e.g. 240 lines/cm can be produced without any difficulty. The ink supply and its consistency across the sheet, as well as throughout the print run, is most important. This is not at all a simple requirement of quality! The ink layer thickness, print-out of the screen dots and their edge definition as well as dot gain (i.e. enlargement of the screen dots by the printing process) and ink trapping (i.e. the interaction of the superimposed ink layers) are some quality-determining characteristics. The slightest position deviations can lead to unacceptable colour deviations. In multi-colour printing, production in-register is essential for a high quality standard. The individual colour separations must fit on top of one another, with an accuracy of 1/100 mm. Deviations results in bluffing and colour deviations.
Press design
Sheetfed printing press, are currently supplied with up to eight printing units (this is required, for example, when using additional special colours/spot colours as well as for perfecting printing) and an additionally integrated varnishing unit. The presses can be equipped also with different types of drying systems. Built-in perfecting devices permit the perfecting of the sheet in the press for printing both sides at full production speed (perfecting printing).
In recent years, in-line coating has become increasingly important in connection with the continuously growing quality demands on printing products, especially in the packaging market. The coating unit shown in is suitable for the large-sized printing of a thin coating application of a thin coating layer, but also for spot coating. For this purpose, a-letterpress plate prepared to suit the parts of the print image to be coated is mounted on the plate cylinder. The coating unit shown in is integrated into an offset press that is designed especially for processing cardboard of about I mm thickness. The special feature of this press, is the size of the paper-transport-ing cylinders. These have an especially large diameter in order to reduce the bending strees on the cardboard and to guarantee a non-smear paper run. High printing speeds, and fast finishing as well as the quality requirements often given rise to the need for in-line drying shows a dryer in the delivery area of the press. By application of energy, the. drying of the ink is accelerated, or wholly realized, before the sheet is collected in the pile. Both IR and UV dryers can be used and adapted in the press.
Sheeters were developed to permit the use of reel paper on sheetfed presses.
The reel paper is wound-off with a special device, cut to individual, correctly-sized sections, and supplied directly to the feeder for the online finishing as a typical feature of sheetfed presses.
Productivity is determined mainly be, the downtimes of the press. Such downtimes or unproductive times are due mainly to plate changes carried out from one job to the next. During the last two years, the press manufacturers have turned their attention especially to developing concepts aimed at simplifying plate supply and clamping. Already in 1991, at an international exhibition in Tokyo (IGAS9 1), Heidelberger Druckmaschinen AG presented a highly-automated sheetfed press. In this press, the individual printing units are equipped with cassettes in which plates prepared for several jobs can be stored. Upon completion of A job, the plate is removed automatically from the plate cylinder and the plate for the next job supplied automatically.
It is due mainly to electrical and electronic engineering that today’s presses can produce at their high standards of productivity and quality. Electronics support and, impart, replace mechanical functions and permit the safe, comfortable, and centralized press operation, shows the central control console of a multi-colour sheetfed offset press. The ink flow, circumferential and lateral colour register are set from there.
Remote Control Console for a small-colour sheet fed press. Model CPC with CP Tronic.
Measuring and control tecniques
Shows press automating components. The CPC I control console was explained already in Fig. 7 (CPC stadns for Computer Print Control). The simplification and precission on ink-key presetting considerably reduces makeready times. For this purcpose, plate readers are used (at Heidelbery. CPC 3 as shown in Fig. 8 Before plating in carried out in the press, an opto-electrical measuring device calculates the ink requirements for the individual in keys. The corresponding data are written on a cassette that is then read-in at the CPC Control console for press presetting.
Components for measuring printing quality are the CPC 2-S print quality, measuring system and the CPC 4 register mark reader for the objective calculation of the printing quality and press control. Special small register marks are pri
